Class U, V and W were given some sweets to sell for their fund-raising project. The average number of sweets the 3 classes had at first was 248. After Class V sold thrice as many sweets as Class U and Class W sold ⁴₅ as many sweets as Class V, the average number of sweets the 3 classes had left was 56. How many sweets did Class U and Class W sell altogether?

Class U	Class V	Class W
1x5	3x5
	5x3	4x3
5 u	15 u	12 u

Class U : Class V : Class W
5 : 15 : 12

Total number of sweets that the 3 classes had at first
= 3 x 248
= 744

Number of sweets that the 3 classes left
= 3 x 56 
= 168

Number of sweets that were sold by 3 classes
= 744 - 168
= 576

5 u + 15 u + 12 u = 576
32 u = 576

1 u = 576 ÷ 32 = 18

Total number of sweets sold by Class U and Class W
= 5 u + 12 u
= 17 u
= 17 x 18
= 306

Answer(s): 306